Antigenic relationships among frog viruses demonstrated by the plaque reduction and neutralization kinetics tests

Antigenic characterization of a marine fish iridovirus from grouper, Epinephelus spp

Iridoviruses, recognized as causative agents of serious systemic diseases, have been identified from more than 20 fish species. Antigenic properties of a pathogenic iridovirus isolated from grouper, Epinephelus spp., in Singapore (SGIV) were investigated using rabbit IgG against the virus. Antisera were prepared by immunization of rabbit with purified virions. The rabbit IgG was purified from antiserum using a protein A-agarose column and adsorbed onto acetone-dried grouper (GP) cells. The viral surface-exposed antigens were visualized by a combination of immunogold transmission electron-microscopy and by indirect immunofluorescence, and the viral antigenic related proteins were discriminated by Western blot. The cross immunofluorescence assay showed that the grouper virus isolate was serologically close to viruses of the genus Ranavirus of family Iridoviridae. The viral antigens were detected from virus infected-cell cultures as early as 4 h of post infection using IFAT, and could be detectable in virus-infected fish blood as early as 3 days post infection. Immuno-dot assays revealed that the rabbit anti-SGIV IgG allowed sensitive detection of SGIV viral antigens. This study will facilitate the development of diagnostic techniques and vaccines for grouper iridovirus.

Iguana virus, a herpes-like virus isolated from cultured cells of a lizard, Iguana iguana

An agent cytopathic for Terrapene and Iguana cell cultures was isolated from spontaneously degenerating cell cultures prepared from a green iguana (Iguana iguana). The agent, designated iguana virus, caused a cytopathic effect (CPE) of a giant cell type, with eosinophilic inclusions commonly observed within giant cell nuclei. Incubation temperature had a marked effect on CPE and on virus release from infected cells. Within the range of 23 to 36 C, low temperatures favored CPE characterized by cytolysis and small giant cell formation, and significant virus release was observed. At warmer temperatures, a purely syncytial type of CPE and total absence of released virus were noted. A unique type of hexagonal eosinophilic cytoplasmic inclusion was observed within syncytia of infected Terrapene cell cultures incubated at 36 C. In vivo studies revealed no evidence of pathogenicity of iguana virus for suckling mice, embryonated hen's eggs, or several species of reptiles and amphibians. Inoculation of iguana virus into young iguanas consistently caused infection that was "unmasked" only when cell cultures were prepared directly from the infected animal. Filtration studies revealed a virion size of >100 nm and <220 nm. Iguana virus is ether-sensitive and, as presumptively indicated by studies of inhibition by bromodeoxyuridine, possesses a deoxyribonucleic type of nucleic acid. The virus characteristics described, as well as electron microscopy observations described in a separate report, indicate that iguana virus is a member of the herpesvirus group.